The preparation which is the subject of inquiry differs from most of the weapons given us in our combat with disease in that its discovery was not due to a lucky accident but was rather the result of a carefully worked out method of investigation.
Believing that for each specific parasite a specific curative drug could be found, Ehrlich set out to find a Substance which should be should be parasitotropic to the Spirochœta pallida (that is, should enter into combination with the pathogenic-orgorganism), rather than organotropic (that is, capable of combining with the cells of the human body). The direction which his search should take in syphilis had already been indicated by the work with atoxyl that had been done by Uhlenhuth, who had found that that substance permanently cured the syphilis of rabbis. In the clinical use of atoxyl, its effects on the body had been found so
HIRSCHFELDER JO. THE USE OF SALVARSAN. JAMA. 1911;LVII(21):1667-1670. doi:10.1001/jama.1911.04260110167005